When a locomotive of a train passes through a long tunnel, the exhaust of the locomotive engine pollutes the air in the tunnel by reducing the oxygen therein and increasing the concentration of carbon monoxide and other exhaust constituents. This pollution can be deleterious, especially where the train includes two or more locomotives, which is a common occurrence where long trains are utilized and/or some of the roadway extends at a steep incline. In such a case, the air intake of the second locomotive sucks in air containing a high proportion of the hot exhaust from the first locomotive, resulting in greatly diminished power output from the second locomotive and causing the second locomotive to overheat. The reduced output results in poor fuel efficiency, and this and the overheating results in the possibility of stalling of the train. Large fans can be utilized to ventilate the tunnel, but they have only a low effectiveness.